Java中初始化数据域的四种方法
1.在构造器中设置值

/** *  */package jry;/** * @author freewill * @desc 初始化块 Core Java page124 */public class InitFiledByBlock {private static int nextId;private int id;private String name;private double salary;public InitFiledByBlock(String n, double s) {this.name = n;this.salary = s;}public int getId() {return id;}public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public double getSalary() {return salary;}public void setSalary(double salary) {this.salary = salary;}{id = nextId;nextId++;}/** * @param args * @desc Testcase */public static void main(String[] args) {InitFiledByBlock c = new InitFiledByBlock("Jordan", 2300);System.out.println(c.getId() + c.getName() + c.getSalary());InitFiledByBlock d = new InitFiledByBlock("James", 2000);System.out.println(d.getId() + d.getName() + d.getSalary());}}

补充知识：调用构造器的具体处理步骤
所有数据域被初始化为默认值(0、false、null)
按照在类声明中出现的次序，依次执行所有域初始化语句和初始化块
如果构造器第一行调用了第二个构造器，则执行第二个构造器主体
执行这个构造器的主题
see Core Java page125